North Korea said Monday that it would release seven South Korean crew members and their fishing boat, a month after they were taken into custody after Pyongyang said they had violated its maritime border.

State media called the violation 'an intolerable infringement upon the sovereignty' of North Korea but the government decided to release the four South Koreans and three Chinese after they had confessed to sailing into North Korea's exclusive economic zone off its east coast.

The decision to release the men was made on 'patriotic and humanitarian grounds,' the reports said.

The fishing boat was intercepted Aug 8 and taken to a North Korean port. South Korea then asked repeatedly for the crew's release.

South Korea's unification ministry said North Korea had informed it that it would make a sea handover of the boat Tuesday.

The release comes at a time of heightened tension on the Korean Peninsula. South Korea blamed its neighbour for sinking one of its warships in March, killing 46 sailors. The North has denied involvement in the sinking.